1. Technical Field
The present invention relates to a process for manufacturing a probe that is designed to interact with a storage medium and to a probe thus obtained.
2. Description of the Related Art
As is known, storage systems that exploit a technology based upon magnetism, such as, for example, hard disks, suffer from important limitations as regards the increase of the data-storage capacity and the read/write rate, and the reduction in their dimensions. In particular, a physical limit exists, the so-called “superparamagnetic limit”, which hinders the dimension reduction of the magnetic storage domains below a critical threshold, if the risk of losing the stored information is to be avoided.
In the last few years, alternative storage systems have consequently been proposed, amongst which the so-called “probe-storage systems” (also referred to as “atomic-level storage systems” or “atomic storage systems”) have assumed particular importance. These systems enable high data-storage capacities on media of small dimensions and with low production costs to be achieved.
In brief, FIG. 1, a probe-storage device 1 comprises a two-dimensional array of transducers (or probes) 2, fixed to a common substrate 3, for example of silicon. The array is arranged on top of a storage medium 4 and is mobile relatively to the storage medium, generally in two mutually orthogonal directions, by the action of a micromotor associated therewith. Each probe 2 is equipped with a supporting element 5 of semiconductor material, in particular silicon, generally known as “cantilever”, suspended in cantilever fashion on top of the storage medium 4, and carrying at one free end thereof an interaction element (also referred to as “sensor” or “contact element” and referred to hereinafter as “tip” 6) facing the storage medium 4. In particular, herein the term “interaction” includes any operation of reading, writing or erasing that implies an exchange of signals between the tip 6 and the storage medium. Via the respective tip 6, each probe 2 is able to locally interact with a portion of the storage medium, for writing/reading/erasing individual bits of information.
The physical characteristics (hardness, roughness, etc.), morphological characteristics (dimensions, shape, etc.) and electrical characteristics (resistivity, thermal conductivity, etc.) of the tip 6 are strictly correlated to the material of the storage medium with which they are associated (polymeric, ferroelectric, phase-change material, etc.), and to the interaction mechanisms for reading/writing/erasing data (thermal process, passage of charge, etc.).
For example, storage systems of the probe-storage type are possible, wherein reading/writing of the individual bits is performed by interacting with the storage material via a passage of electrical charges through the tip.
Currently, some proposed solutions use a polymeric material for storage of the data, and silicon tips (coated with native oxide) for providing the interaction structure. However, the polymeric material does not enable passage of electrical charges. To overcome this problem, it is possible to deposit a very thin conductive layer on top of the silicon tip (after removal of the native oxide). However, this solution has not proven practically feasible, in so far as the silicon tip is formed only at the end of the integration process so as to protect the silicon tip while forming the cantilever structure and bonding the wafers. Furthermore, the deposition of a thin layer of conductive material causes an increase in the tip radius with respect to the original tip dimension, thus reducing the obtainable storage density. In fact, if the storage area is, for example, 1 cm2, it is necessary to mold and etch features of 10 nm to obtain a memory of 50 GB.